Solid state lasers, such as those constructed of a material known as Nd: YAG, neodymium doped yttrium aluminum garnet, can be stimulated to produce a lasing beam with a light pump. For example, as described in the U.S. Pat. No. 3,624,545 to Ross, a plurality of diode lasers are directed onto a rod shaped Nd: YAG main laser element to stimulate it into a lasing operation. The diode lasers are directed at a side of the main laser element and are provided in sufficient quantity to provide the pumping power necessary to produce pulsed lasing.
The side pumped Ross type laser involves a larger number of diode lasers to obtain the desired pump power needed to stimulate the main laser. The coupling efficiency for this configuration is low because the relatively small diameter of the Nd:YAG laser rod exposed to the pump source limits the effective optical path length of the pump light.
In an article entitled "GaAs Diode Pumped Nd:YAG Laser" by one of the inventors, L. J. Rosenkrantz published in the Journal of the Applied Physics, Vol. 43, No. 11 of November, 1972 at page 4603, a laser is described wherein a diode laser is employed to pump a rod-shaped main laser. The diode laser is directed at an axial end of the main laser to produce laser pulses. The end pumping approach as described in this article increases the absorption of the pumping light by the main laser which thus provides a lasing response at a lower diode laser pump source power level.